TM 808 White's

[berreizeta]

I have finally managed to make a 4060 that work. (10 units in the trash, bad or fake?...)

With 10k and 220p it gives me 6600 Hz

[Skippy]

Gotta say, I'm not sure what you're doing with the '4060.
The idea of the 4060 ( or another 4024 ) was to divide down the signal from a STABLE high-frequency source, such as a quartz crystal ( ideal ) , or a ceramic resonator ( OK, but not so accurate or stable ). These all run at 100 kHz to 10 MHz, so need plenty of dividing down to get 26370 Hz ( = 4 x 6.59 kHz ). The 26370 Hz is fed into the 4024 divider, to make 6.59kHz, and other lower multiples for audio tone generation etc.
I suggested two possibilities: a 6.7458 MHz quartz crystal, divided down by 256 gives 26351 Hz, and a correct coil frequency of 6.588 kHz;
or a ceramic resonator of 420 kHz, divided by 16 to give 26250 Hz, and a detector frequency of 6.563 kHz. A 429 kHz resonator would also be close enough.
Both of these options should work with the '4060 chip, when operated at 15 Volts supply, the same as all the other logic IC's in the detector. The resonator will definitely work, the 6.7458 MHz crystal is getting towards the limit for this IC. ( IC's vary; different manufacturers, different age of the part, lots of unknowns ).
Other circuit options include:
Using the existing two NAND gates to make an oscillator with the 420 kHz resonator or 6.7458 MHz crystal. Then use a seperate divider chip, either the '4060, or a '4024, to create the 26370 Hz frequency. This would be OK for the 420k resonator, but the 6.74.. MHz crystal may be too high for a NAND based oscillator.
What you should NOT be doing is messing around with crappy R-C oscillators. There are ways to make decent R-C oscillators, but a 4060 inverter based one is not a decent one.

My honest suggestion is to use the existing two NAND gates to make a 420 kHz resonator oscillator / buffer. Feed the output of that into a CD4024 divider IC. Use the Q4 output ( divide by 16 ), and feed that into Input ( pin 1 ) of the '4024 in the existing circuit.
Sure, the 420 kHz resonator is a bit tricky to get ( it's obsolete, but was very common ), so you may have to settle on the 429 KHz version, which is much more easily found.

[Skippy]

As an additional thought: you could make the oscillator selectable between 420 kHz and 429 kHz, for example by using a 3-pin header, and a jumper link that you place in one of two positions. Use either 2mm pitch or 0.1 inch pitch, depending on space available.
This could be useful if you are having interference problems - sometimes a small change in detector frequency is enough to quieten it down.

[Skippy]

I've just discovered these ceramic resonators are also made for 426 kHz, intended for TV remote control use, again. So that's another alternative option.

[berreizeta]

At the moment I don't have anything else to "play",

I can't get the 420, 429 is easy to get and is another viable option

The 4060 I'm seeing is less stable than a 7555, is ruled out

I am waiting for the 25600 crystals, which for me is still the best option 25600/4 = 6400 Hz

I keep doing tests with the coils but I have doubts about the values: 175mH for RX and 645uH for TX ?

[Skippy]

"The '4060 I'm seeing is less stable than a 7555 timer" The '4060 just has an inverter at the heart of it's oscillator. It's never going to be any good used as an R-C oscillator. But ICL7555 CMOS timers are pretty rubbish, too, don't use them. By far the best of the "555" devices are the LinCMOS parts, like the TLC555. They are fast, low power, don't get warm and drift about. They even have reasonable output current capability ( pin 3 ). The maximum supply voltage is lower than the bipolar ( NE555 ) version, worth remembering.
By the way, the 25600 Hz crystal module is likely to be a 3.276800 Mhz crystal, divided down by 128. This crystal freq is widely used in timing circuits, if you divide it down more, you get 100 Hz, useful for decimal timers, like stopwatches.

[berreizeta]

3.2768 Mhz easy to find :

[Skippy]

If you built your own oscillator / divider using the 3.2768 MHz crystal, it would be powered from the 15V supply, so it would not need additional voltage-shifting transistors etc to connect to the existing circuit ( which your module would need ).
It would also work with either the NAND gate oscillator circuit, plus a '4024 divider ....
.... or with the '4060 oscillator / divider chip.

An additional idea:
If you layout your PCB so you can select between two different Q outputs from a divider IC ( for example with a wire link ), you would have the option of using a 3.2768 MHz crystal ( to make 25600 Hz and then -> 6400 Hz ) or .. use a 6.7458 MHz crystal ( to make 26351 Hz and then -> 6588 Hz ).

[Skippy]

For info, here is a technical guide to using ceramic resonators. It includes suggested component values for a simple 4000-series inverter-based oscillator. https://ecsxtal.com/127-ceramic-resonator-principles/

[berreizeta]

Received xtal 25.6Khz

Aliexpress, I have found a seller who has offered me 420Khz ceramics for sale:

https://es.aliexpress.com/item/10050....0.0.7c4a7a9dn 3dXuO&mp=1&gatewayAdapt=glo2esp

[Skippy]

I've looked into what frequencies these ceramic resonators have as "standard" values, in the 420-430 kHz range. They are:
420 kHz : not common, obsolete, used in remote controls, divide by 12 -> 35 kHz
421 kHz : very rare
425 kHz : seems unavailable
426 kHz : rare, but available
429 kHz : common, remote controls, divide by 12 -> 35.75 kHz, a near-enough match to 36 kHz
432 kHz : common, remote controls, divide by 12 -> 36 kHz exactly

I'm thinking that 429 kHz would be a sensible choice as a "primary" frequency, and the choice of 432 kHz or 426 kHz as secondary options. These two alternatives are 0.7% above and below the 429k frequency. This would make the detector operate at 6703 Hz ( and +/- 0.7% ).
Regarding availability:
429k and 432k are pretty easy to find.
A UK seller, Continental Electronics, has 429k, 432k,( and two different 420 kHz types ). His shop :
https://www.ebay.co.uk/itm/255143325489
https://www.continentelec.co.uk/
The 426k part is available from Cricklewood Electronics in the UK:
https://www.cricklewoodelectronics.com/D426.html
There's this German seller, who also lists 420k, 429k :
https://www.williges-elektronik.de/4...resonator.html

Running the detector at 6703 Hz instead of 6590 Hz means you will need 3.5% less tuning capacitance on the coil ... or 3.5% less inductance in the coil windings.

[berreizeta]

The tests I've done with the 25.6Khz xtal lead me to add: a 78L33 (3.3v) to power the crystal

and a LM386 to raise the crystal signal to +-10V,

otherwise the 4024 at 16v won't work with xtal signal = 3.3 or 5V.

[Skippy]

Yes, see my post number 152. Your module generates a digital signal, the '4024 divider chip needs a digital signal. So you need a digital circuit, usually known as a "level shifter" to interface 3V3 ( or 5V ) signals to 15V signals. Luckily, the frequency of 26 kHz is pretty low, so that makes your level-shifter design simpler; fast switching circuits are usually more complex.
To save me the bother of drawing circuits and uploading them ( I have major problems with this new VBulletin 5.7 ), I will link to this article:
https://next-hack.com/index.php/2020...to-a-5v-input/
Figures 10, 11, 12 are the sort of schemes to use, just replace the +5V supply with the +7.5V.
There are other alternatives. If you use the virtual 0 Volt supply, you could power the osc module from a 5V regulator fed from +7.5V and 0V. Then a high-side pnp transistor based switch will switch between +5V and -7.5V, which is good enough to feed into a 4024 powered from +7.5V and -7.5V.
... that one needs a drawing, I guess.
That's why I said building your own 3.2768 MHz oscillator / divider, powered from 15V ( +7.5 and -7.5 ) would be a neater way of doing it.

[berreizeta]

Done !
In the collector of Q1 I have 6.4Khz
With 15-16v the signal loses a couple of volts, maximum signal at 10-12v.
Why are 15 volts needed and it is not powered at 12v?
Tested with a small coil tuned close to 6400Hz *6398.4* and the Visual Analyzer program.

[Skippy]

A curious observation. Normally, I would say 15V ( +/- 7.5V ) was chosen because that is near the maximum supply voltage for CD4000 series parts, and they perform best with higher voltages - faster switching, more drive current from the output, lower ON-resistance of analogue switches ( 4053, 4066 etc ) etc. And analogue circuits are able to handle higher level signals. Plus, back when this circuit was designed, a 15V analogue supply was quite normal; op-amps for 5 V or 3.3V operation were rare, so no-one would intentionally choose a low supply voltage, unless low power consumption was a design requirement.
The purpose of transistor Q1 is as a current source. The 4.3 V zener diode means the base voltage is fixed when it's turned on, and so the emitter is also reasonably fixed, 0.65V higher. So the 51 Ohm resistor has a steady ( 4.3 - 0.65 ) = 3.65V across it, and so passes a current of 72 mA. This should be the same for 12V or 15V supply.
One difference is the base current drive, through the 2K7 resistor. At 15V supply, there should be (15 - 4.3 ) / 2700 = 4 mA. At 12V, this drops to 2.9 mA. This may be important.
One experiment to try : test the circuit at 15V, with the 2k7 resistor. Then test it at 12V, but with a 2k0 resistor. These are both giving 4 mA base current. You could also try 15V and a 3k6 resistor, which gives 2.9 mA base current, and compare to 12V / 2k7 .
I believe the sinewave voltage on the coil is 'clamped' by the conduction of the transistor collector-base diode. The clamping is affected by the 2k7 resistor, and the zener diode, which forward conducts with 0.65V drop to the +ve supply rail.

On a different subject : I see your toroid is a bright green colour. Is this one you bought, to a particular specification, or is it a salvaged part ? It looks like a typical "common mode choke" , found on mains power supply filters in many circuits. If this is so, it may not be the best choice of ferrite material, as it is designed to absorb energy at 'high' frequencies. High may be just a few kHz, they are designed to pass 50 / 60 Hz, anything else can be filtered . They are probably not the best choice for this detector.